Toshihiko Itesako

Aberrant expression of microRNAs in bladder cancer

MicroRNAs (miRNAs), a class of small noncoding RNAs, regulate protein-coding gene expression by repressing translation or cleaving RNA transcripts in a sequence-specific manner. A growing body of evidence suggests that miRNAs contribute to bladder cancer development, progression and metastasis. Genome-wide miRNA expression signatures have been used to rapidly and precisely identify aberrant miRNA expression in bladder cancer. Based on reports describing miRNA signatures, several downregulated and upregulated miRNAs have been discovered. Examination of the differential expression of miRNAs between clinical bladder cancer and normal bladder tissue has led to the elucidation of 11 miRNA expression signatures. miRNAs downregulated in bladder cancer, such as miR-145, miR-143 and miR125b, are known to be tumour suppressors, whereas upregulated miRNAs, such as miR-183, miR-96, miR17-5p and miR-20a are oncogenic. Several studies have demonstrated the potential of miRNAs for providing prognostic information. miR-145 is the most frequently downregulated miRNA in bladder cancer and has been shown to significantly inhibit proliferation, migration and invasion. Understanding the role of differentially expressed miRNAs, as well as their molecular targets, in bladder cancer will provide an effective and promising strategy for miRNA-based therapeutics for the treatment of bladder cancer.

Tumor‐suppressive microRNA‐143/145 cluster targets hexokinase‐2 in renal cell carcinoma

Our recent studies of microRNA (miRNA) expression signatures have indicated that the miR‐143/145 cluster is significantly downregulated in several types of cancer and represents a putative tumor‐suppressive miRNA in human cancers. The aim of this study was to investigate the functional significance of the miR‐143/145 cluster in cancer cells and to identify novel molecular targets of the miR‐143/145 cluster in renal cell carcinoma (RCC). The expression levels of miR‐143 and miR‐145 were significantly downregulated in RCC tissues compared with adjacent non‐cancerous tissues. A significant positive correlation was recognized between miR‐143 and miR‐145 expression. Restoration of mature miR‐143 or miR‐145 in 786‐O and A498 RCC cells revealed that both mature miRNAs significantly inhibited cancer cell proliferation and invasion, suggesting that the miR‐143/145 cluster functioned as a tumor suppressor in RCC. Gene expression data and in silico database analysis showed that the hexokinase‐2 (HK2) gene, which encodes a glycolytic enzyme crucial for the Warburg effect in cancer cells, was a candidate target of the miR‐143/145 cluster. Luciferase reporter assays showed that both miR‐143 and miR‐145 directly regulated HK2. In RCC clinical specimens, the expression of HK2 was significantly higher in cancer tissues than in non‐cancerous tissues. Silencing HK2 suppressed RCC cell proliferation and invasion, suggesting that HK2 has oncogenic functions in RCC. Thus, our data showed that loss of the tumor‐suppressive miR‐143/145 cluster enhanced RCC cell proliferation and invasion through targeting HK2.

The tumor-suppressive microRNA-143/145 cluster inhibits cell migration and invasion by targeting GOLM1 in prostate cancer

Our recent study of microRNA (miRNA) expression signature of prostate cancer (PCa) has revealed that the microRNA-143/145 (miR-143/145) cluster is significantly downregulated in cancer tissues, suggesting that these cluster miRNAs are candidate tumor suppressors. The aim of this study was to investigate the functional significance of the miR-143/145 cluster in PCa cells and to identify novel targets regulated by these cluster miRNAs in PCa. Restoration of miR-143 or miR-145 in PCa cell lines (PC3 and DU145) revealed that these miRNAs significantly inhibited cancer cell migration and invasion. Gene expression data and in silico analysis demonstrated that Golgi membrane protein 1 (GOLM1) resembling a type II golgi transmembrane protein was a potential target of miR-143/145 cluster target gene. Gene expression studies and luciferase reporter assays showed that GOLM1 was directly regulated by the miR-143/145 cluster. Silencing of GOLM1 resulted in significant inhibition of cell migration and invasion in PCa cells. Furthermore, the expression of GOLM1 was upregulated in cancer tissues by immunohistochemistry. Loss of the tumor-suppressive miR-143/145 cluster enhanced cancer cell migration and invasion in PCa through directly regulating GOLM1. Our data on target genes regulated by the tumor-suppressive miR-143/145 cluster provide new insights into the potential mechanisms of PCa oncogenesis and metastasis.

The MicroRNA Expression Signature of Bladder Cancer by Deep Sequencing: The Functional Significance of the miR-195/497 Cluster

Current genome-wide microRNA (miRNA) expression signature analysis using deep sequencing technologies can drive the discovery of novel cancer pathways regulated by oncogenic and/or tumor suppressive miRNAs. We determined the genome-wide miRNA expression signature in bladder cancer (BC) by deep sequencing technology. A total of ten small RNA libraries were sequenced (five BCs and five samples of histologically normal bladder epithelia (NBE)), and 13,190,619 to 18,559,060 clean small RNA reads were obtained. A total of 933 known miRNAs and 17 new miRNA candidates were detected in this analysis. Among the known miRNAs, a total of 60 miRNAs were significantly downregulated in BC compared with NBE. We also found that several miRNAs, such as miR-1/133a, miR-206/133b, let-7c/miR-99a, miR-143/145 and miR-195/497, were located close together at five distinct loci and constituted clustered miRNAs. Among these clustered miRNAs, we focused on the miR-195/497 cluster because this clustered miRNA had not been analyzed in BC. Transfection of mature miR-195 or miR-497 in two BC cell lines (BOY and T24) significantly inhibited cancer cell proliferation, migration and invasion, suggesting that the miR-195/497 cluster functioned as tumor suppressors in BC. Regarding the genes targeted by the miR-195/497 cluster, the TargetScan algorithm showed that 6,730 genes were putative miR-195/497 targets, and 113 significantly enriched signaling pathways were identified in this analysis. The “Pathways in cancer” category was the most enriched, involving 104 candidate target genes. Gene expression data revealed that 27 of 104 candidate target genes were actually upregulated in BC clinical specimens. Luciferase reporter assays and Western blotting demonstrated that BIRC5 and WNT7A were directly targeted by miR-195/497. In conclusion, aberrant expression of clustered miRNAs was identified by deep sequencing, and downregulation of miR-195/497 contributed to BC progression and metastasis. Tumor suppressive miRNA-mediated cancer pathways provide new insights into the potential mechanisms of BC oncogenesis.

MicroRNA-218 Inhibits Cell Migration and Invasion in Renal Cell Carcinoma through Targeting Caveolin-2 Involved in Focal Adhesion Pathway

PURPOSE Our microRNA expression signature of renal cell carcinoma revealed that miR-218 expression was significantly decreased in cancer tissues, suggesting that miR-218 is a candidate tumor suppressor. We investigated the functional significance of miR-218 in cancer cells and identified what are to our knowledge novel miR-218 mediated cancer pathways in renal cell carcinoma. MATERIALS AND METHODS Gain of function studies using mature miR-218 were performed to investigate cell proliferation, migration and invasion in the A498 and 786-O renal cell carcinoma cell lines. To identify miR-218 mediated molecular pathways and responsible genes in renal cell carcinoma, we used gene expression and in silico database analyses. Loss of function assays were performed to investigate the functional significance of miR-218 target genes. RESULTS Restoration of mature miR-218 significantly inhibited RCC cell proliferation, migration and invasion. Gene expression studies and luciferase reporter assays showed that CAV2 involved in the focal adhesion pathway was directly regulated by miR-218. A silencing study of CAV2 revealed significant inhibition of cell proliferation, migration and invasion. CAV2 mRNA and protein expression was significantly up-regulated in renal cell carcinoma clinical specimens. CONCLUSIONS Loss of tumor suppressive miR-218 enhances cancer cell migration and invasion through dysregulation of the focal adhesion pathway, especially CAV2 as an oncogenic function in renal cell carcinoma. Tumor suppressive microRNA mediated cancer pathways and responsible genes provide new insights into the potential mechanisms of renal cell carcinoma oncogenesis and metastasis.

Tumor suppressive microRNA-218 inhibits cancer cell migration and invasion by targeting focal adhesion pathways in cervical squamous cell carcinoma

Cervical cancer is one of the most common cancers in women. More than 275,100 women die from cervical cancer each year. Cervical squamous cell carcinoma (cervical SCC), one of the most frequent types of cervical cancers, is associated with high-risk human papilloma virus (HPV), although HPV infection alone may not be enough to induce malignant transformation. MicroRNAs (miRNAs), a class of small non-coding RNAs, regulate protein-coding gene expression by repressing translation or cleaving RNA transcripts in a sequence-specific manner. A growing body of evidence suggests that miRNAs contribute to cervical SCC progression, development and metastasis. miRNA expression signatures in SCC (hypopharyngeal SCC and esophageal SCC) revealed that miR-218 expression was significantly reduced in cancer tissues compared with adjacent non-cancerous epithelium, suggesting that miR-218 is a candidate tumor suppressor. The aim of this study was to investigate the functional significance of miR-218 in cervical SCC and to identify novel miR-218-mediated cancer pathways in cervical SCC. Restoration of miR-218 significantly inhibited cancer cell migration and invasion in both HPV-positive and HPV-negative cervical SCC cell lines. These data indicated that miR-218 acts as a tumor suppressor in cervical SCC. Our in silico analysis showed that miR-218 appeared to be an important modulator of tumor cell processes through suppression of many targets, particularly those involved in focal adhesion signaling pathways. Gene expression data indicated that LAMB3, a laminin protein known to influence cell differentiation, migration, adhesion, proliferation and survival, was upregulated in cervical SCC clinical specimens, and silencing studies demonstrated that LAMB3 functioned as an oncogene in cervical SCC. The identification of novel tumor-suppressive miR-218-mediated molecular pathways has provided new insights into cervical SCC oncogenesis and metastasis.

Tumour-suppressive microRNA-29s inhibit cancer cell migration and invasion by targeting laminin–integrin signalling in head and neck squamous cell carcinoma

Background:Our recent studies of microRNA (miRNA) expression signatures demonstrated that microRNA-29s (miR-29s; miR-29a/b/c) were significantly downregulated in head and neck squamous cell carcinoma (HNSCC) and were putative tumour-suppressive miRNAs in human cancers. Our aim in this study was to investigate the functional significance of miR-29s in cancer cells and to identify novel miR-29s-mediated cancer pathways and responsible genes in HNSCC oncogenesis and metastasis.Methods:Gain-of-function studies using mature miR-29s were performed to investigate cell proliferation, migration and invasion in two HNSCC cell lines (SAS and FaDu). To identify miR-29s-mediated molecular pathways and targets, we utilised gene expression analysis and in silico database analysis. Loss-of-function assays were performed to investigate the functional significance of miR-29s target genes.Results:Restoration of miR-29s in SAS and FaDu cell lines revealed significant inhibition of cancer cell migration and invasion. Gene expression data and in silico analysis demonstrated that miR-29s modulated the focal adhesion pathway. Moreover, laminin γ2 (LAMC2) and α6 integrin (ITGA6) genes were candidate targets of the regulation of miR-29s. Luciferase reporter assays showed that miR-29s directly regulated LAMC2 and ITGA6. Silencing of LAMC2 and ITGA6 genes significantly inhibited cell migration and invasion in cancer cells.Conclusion:Downregulation of miR-29s was a frequent event in HNSCC. The miR-29s acted as tumour suppressors and directly targeted laminin–integrin signalling. Recognition of tumour-suppressive miRNA-mediated cancer pathways provides new insights into the potential mechanisms of HNSCC oncogenesis and metastasis and suggests novel therapeutic strategies for the disease.

Epithelial–mesenchymal transition-related microRNA-200s regulate molecular targets and pathways in renal cell carcinoma

Our recent studies of microRNA (miRNA) expression signatures demonstrated that the epithelial–mesenchymal transition (EMT)-related microRNA-200 family (miR-200s: miR-200a/b/c, miR-141 and miR-429) were significantly downregulated in renal cell carcinoma (RCC) and putative tumor-suppressive miRNAs in RCC. In this study, our aim was to investigate the functional significance of the miR-200s in cancer cells and to identify novel miR-200s-regulated molecular targets and pathways in RCC. Expression levels of all the miR-200s members were significantly downregulated in human RCC tissues compared with normal renal tissues. Restoration of mature miR-200s in RCC cell line resulted in significant inhibition of cell proliferation and migration, suggesting that miR-200s function as tumor suppressors in RCC. Furthermore, we utilized gene expression analysis and in silico database analysis to identify miR-200s-regulated molecular targets and pathways in RCC. The miR-200s was categorized into two groups, according to their seed sequences, miR-200b/c/429 and miR-200a/141. Our data demonstrated that the ‘Focal adhesion’ and ‘ErbB signaling’ pathways were significantly regulated by miR-200b/c/429 and miR-200a/141, respectively. The identification of novel tumor-suppressive miR-200s-regulated molecular targets and pathways has provided new insights into RCC oncogenesis and metastasis.

Tumor-suppressive microRNA-135a inhibits cancer cell proliferation by targeting the c-MYC oncogene in renal cell carcinoma.

Recently, many studies have suggested that microRNAs (miRNAs) are involved in cancer cell development, invasion, and metastasis of various types of human cancers. In a previous study, miRNA expression signatures from renal cell carcinoma (RCC) revealed that expression of microRNA‐135a (miR‐135a) was significantly reduced in cancerous tissues. The aim of this study was to investigate the functional significance of miR‐135a and to identify miR‐135a‐mediated molecular pathways in RCC cells. Restoration of mature miR‐135a significantly inhibited cancer cell proliferation and induced G0/G1 arrest in the RCC cell lines caki2 and A498, suggesting that miR‐135a functioned as a potential tumor suppressor. We then examined miR‐135a‐mediated molecular pathways using genome‐wide gene expression analysis and in silico analysis. A total of 570 downregulated genes were identified in miR‐135a transfected RCC cell lines. To investigate the biological significance of potential miR‐135a‐mediated pathways, we classified putative miR‐135a‐regulated genes according to the Kyoto Encyclopedia of Genes and Genomics pathway database. From our in silico analysis, 25 pathways, including the cell cycle, pathways in cancer, DNA replication, and focal adhesion, were significantly regulated by miR‐135a in RCC cells. Moreover, based on the results of this analysis, we investigated whether miR‐135a targeted the c‐MYC gene in RCC. Gain‐of‐function and luciferase reporter assays showed that c‐MYC was directly regulated by miR‐135a in RCC cells. Furthermore, c‐MYC expression was significantly upregulated in RCC clinical specimens. Our data suggest that elucidation of tumor‐suppressive miR‐135a‐mediated molecular pathways could reveal potential therapeutic targets in RCC.

Tumour-suppressive microRNA-874 contributes to cell proliferation through targeting of histone deacetylase 1 in head and neck squamous cell carcinoma

Background:Our recent studies of microRNA (miRNA) expression signature demonstrated that microRNA-874 (miR-874) was significantly downregulated in maxillary sinus squamous cell carcinoma (MSSCC), and a putative tumour-suppressive miRNA in human cancers. Our aim of this study was to investigate the functional significance of miR-874 in cancer cells and to identify novel miR-874-mediated cancer pathways and responsible genes in head and neck squamous cell carcinoma (HNSCC).Methods:Gain-of-function studies using mature miR-874 were performed to investigate cell proliferation and cell cycle distribution in HNSCC cell lines (SAS and FaDu). To identify miR-874-mediated molecular pathways and targets, we utilised gene expression analysis and in silico database analysis. Loss-of-function assays were performed to investigate the functional significance of miR-874 target genes.Results:Expression levels of miR-874 were significantly downregulated in HNSCC tissues (including oral, pharyngeal and laryngeal SCCs) compared with normal counterpart epithelia. Restoration of miR-874 in SAS and FaDu cell lines revealed significant inhibition of cell proliferation and induction of G2/M arrest and cell apoptosis. Our expression data and in silico analysis demonstrated that miR-874 modulated the cell cycle pathway. Moreover, histone deacetylase 1 (HDAC1) was a candidate target of miR-874 regulation. Luciferase reporter assays showed that miR-874 directly regulated HDAC1. Silencing of the HDAC1 gene significantly inhibited cell proliferation and induced G2/M arrest and cell apoptosis in SAS cells.Conclusions:Downregulation of miR-874 was a frequent event in HNSCC. miR-874 acted as a tumour suppressor and directly targeted HDAC1. Recognition of tumour-suppressive miRNA-mediated cancer pathways provides new insights into the potential mechanisms of HNSCC oncogenesis and suggests novel therapeutic strategies for the disease.